Turn off the water at the valves under the sink, and turn on the faucet to allow the water to drain. Make sure the drains are plugged to prevent small parts from falling in.
Use an Allen wrench to loosen the setscrew on the faucet handle, then remove the handle. Be sure to line up the faucet parts in the order in which you remove them. This will help you remember the correct order for reassembly.
Grab the spout with both hands, and work it back and forth to loosen it. Then remove it from the faucet face. (This may require a little muscle.)
Use the spanner to remove the O-rings, and use needlenose pliers to remove the diverter. Clean any sediment or buildup from the faucet face.
Press the new diverter into place, and install the new O-rings. Install the top O-ring first.
Coat the O-rings with packing grease. (Packing grease withstands high water temperatures and protects the faucet components.)
Press the spout back into place. Use both hands, and press firmly. (If you'd like to update the look of your faucet, consider replacing the spout. Check with the manufacturer to learn what styles are available.)
Use the spanner and Allen wrench as a guide to slide the springs and packing pieces into place.
Place the faucet ball into its slot.
Install the cam and cam packing.
Reinstall the chrome bonnet and handle.
Turn on the water and check for leaks.